The present invention relates to a process for microbiological conversion of sulfur-containing pollutants in waste gases, preferably H.sub.2 S, CS.sub.2 and/or COS, in addition to thio-alcohols, thio-ethers, and thiophenes, into dilute acids and the elimination thereof, especially from waste gases from cellulose fiber manufacture.
Disposal of air mixed with the above-noted pollutants as combustion air in steam generators, or use thereof as aeration medium in waste water clarification plants, are known. However, since the respective oxygen requirement constitutes a quantity-limiting criterion and, as in most cases, the unpurified air or waste gas to be disposed of occurs in much larger quantities, complete disposal of these malodorant waste gases of relatively low noxious gas concentration had been an unsolved problem.
Adsorption methods for the separation of H.sub.2 S and CS.sub.2 from viscose waste gases, are also known. Thus, H.sub.2 S can be adsorbed on coarse-pored, activated carbon impregnated with KI, while CS.sub.2 may be adsorbed on a fine-pored, activated carbon. The regeneration of the S-laden, activated carbon is accomplished with liquid CS.sub.2 ; H.sub.2 SO.sub.4 is washed out with water; and CS.sub.2 is desorbed with water vapor. In another method, carbon low in heavy metals is used for the oxidation of H.sub.2 S. H.sub.2 SO.sub.4 formation in small amounts, is neutralized with NH.sub.3.
Both methods can perform the processing steps of H.sub.2 S-oxidation and CS.sub.2 -adsorption in one adsorber or, for higher concentrations, in two separate adsorbers.
Combination processes are also in use which involve alkali scrubbing for removal of H.sub.2 S and activated carbon adsorption for removal of CS.sub.2.
However, these last-noted methods are unsuitable for the purification of large waste gas streams having low noxious gas concentration.